Emag Integration problem! HELP!

1. May 18, 2010

Bigfoots mum

Now then, im close to shedding a tear with this one.

This integral has been popping up in a few electromag examples iv been doing and i have absolutely no idea whats going on here.

The integral is 1/[(x2+z2)3/2] with respect to x

According to the textbook the answer is x/[z2(x2+z2)1/2]

I initially, without evening really thinking, went straight for -1/(x[x2+z2]1/2)

Any ideas?
Thanks

Last edited: May 18, 2010
2. May 18, 2010

Dickfore

First of all, try to find the partial derivative with respect to x (treating z as a constant parameter) of the textbook's answer. If it gives your integrand, then it is correct. If not, it is wrong.

3. May 18, 2010

Bigfoots mum

Iv used a computer, and it tells me its correct! Otherwise, yes i would have done as you said.

4. May 18, 2010

Dickfore

So, I guess this issue is resolved.

5. May 18, 2010

Bigfoots mum

No its not, my question is why is this integral equal to the quoted answer. I gave my attempt at the answer, which is nothing like the actual answer. Im baffled.

6. May 18, 2010

Dickfore

Oh, so you want to calculate the integral.

Try the substitution $x = z \, \tan(p)$.